Indirect nuclear 15N-15N scalar coupling through a hydrogen bond: dependence on structural parameters studied by
Anežka Křístková1, James R Asher, Vladimir G Malkin
1Institute of Inorganic Chemistry, Slovak Academy of Sciences , Dúbravská cesta 9, SK-84536 Bratislava, Slovakia.
Abstract:
NMR spin-spin couplings through a hydrogen bond in the free-base and protonated forms of the complete series of [(15)N2]-N-methylated 1,8-diaminonaphthalenes have been analyzed using quantum chemistry tools. The dominating role of the overlap of the coupling pathway orbitals has been demonstrated. The correlation of the sum of the (13)C NMR shifts of the naphthalene ring C(1,8) carbons directly attached to the interacting nitrogens with the J(N-N) values and the degree of methylation found earlier by G. C. Lloyd-Jones et al. [Chem.-Eur. J. 2003, 9, 4523] have been reexamined. It has been found that the correlations of J(N-N) and [ΔΣC(1,8)] with the degree of methylation have different reasons. While the former is mostly connected with the structural changes due to the solvent effect, the latter is attributed to the changes in the paramagnetic contributions from the C-N and C-C bonds caused by the replacement of a hydrogen by a methyl group.
Related Concept Videos
¹H NMR: Long-Range Coupling
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
Spin–Spin Coupling: One-Bond Coupling
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
NMR Spectroscopy: Spin–Spin Coupling
2D NMR: Overview of Heteronuclear Correlation Techniques


